Resilient torque meter



E'. S. TAYLOR RESILIENT 'roRQUE METER March 4, 1941.

Filed Jan. 12. 1939 'ATTORNEY Patented Mu. 4, 1941.

UNITED STATES PATENT OFFICE Wright Aeronautical tion of New YorkCorporation,A a corpora- YApplicatie January 12, 1939, serial No.253,419

'a claims.

This invention relates to means for preventing resonant vibration' andparticularly, provides 'a compact apparatus (which may be coordinatedwith a torsional measuring means), by vwhich the resonant torsionalvibrations in a shaft system may be avoided in operating speed rangesofthe system. In shaft systems subject to exciting impulses of variousorders, it is known that resonance of the natural vibration frequenciesof the shaft system with the impulsesiis objectionable and destructive,and the desideratum is to so construct the shaft system that its naturalfrequencies are outside the frequency range of the impulses. This 5 maybe done either by increasing the stiffness o r by increasing theflexibility of the system. In.

l the latter typeof solution for the problem, spring drives of variousforms have been used, the flexibility of the springs being a determiningfactor system. However, where the speed and :torque range'in the systemis great, a metallic spring system becomes excessively bulky and heavy,unless the system permits of the use of long flexible 5 drive shafts. Ifspring couplings or the like be used, the springs necessary to giveproper flexibility along With adequate deflection and spring load toassume the driven load may become larger and heavier than any integralpart of the shaft 0 system itself.

This invention sets out to teach the use of fluids as a spring medium toafford added flexibility in shaft systems, particularly those Whereinweight and bulk is ata premium. In the fluid i5 spring, fluid may -beadded or removed to adjust pressure therein, with changes in drivingload so that little or no allowance need be made for load deection. Ineffect, the stress or more properly, pressure in the fluid spring ischanged '.0 with load while maintaining the deflection constant, asdistinguished from a metallic spring wherein the stress therein can onlyincrease with increases in deection. Thus, the uid springis of nearlyconstant size regardless of load, vibra- L5 tory excursions thereinbeing of small order. In

a metal spring, the vibratory excursions are likewise small, butdeflections due to load are extremely large.

An object of the invention is to -provide a c omi0 pact form ofvibration damper utilizing the resilient compressive characteristics offluids or gases under high pressure for introducing into a power shaftsystem a degree of flexibility sufllcient to greatly lower the naturalfrequencies of 55 the system. i

in evaluating the natural frequency of the shaft (Cl. i4-305) Anotherobject of the invention is to provide a relatively constant volume fluidspring, an associated object being to so coordinate the fluid springarrangement that it may be used as a ment by which natural frequenciesof the shaft l system in the engine may be reduced.

Further objects are to provide alternate means by which either liquid orgaseous springs may be utilized, along with fluid supply means by whichthe apparatus is maintained in an operative condition during engineoperation.

Further objects will become apparent in reading the annexed detaileddescription in connection with the drawing, in which Fig. 1 is afragmentary cross-section through the forward pant of an aircraftengine, comprising a section on the line I-I of Fig. 2;

Fig. 2 is an axial fragmentary section .through the forward part of anengine reduction gear;

Fig. 3 is a section through an alternative arrangement of uid springmechanism, and

Fig. 4 is a fragmentary perspective view of part of the fluid springmechanism.

A large part of the structure of the present invention is similar tothat shown in the copending application of Roland Chilton, Serial No.248,052, -flied December 28, 1938. .I show an engine nose housing Iiisecured, as in conventional aircraft engine practice, to a crankcase,not shown. A bell gear I2 secured to the engine crankshaft, `not shown,forms a driving member which engages a plurality of planet pinions Itjournalled on a backplate I6 integral with a propeller shaft I 8, thepinions Irl meshing with a sun gear 20 journalled through balls 22 Aon arace 24 secured tothe housing Ill, The propeller shaft I8 is journaliedin the housing by the usual bearing 26. i

As may be seen in Fig. 1, the sun gear 20 includes a projecting torquearm 28 engageable at one end with a tangentially disposed adjustablestop 30, while a strut 32 is engaged in a counterbore in the arm 28, the'strut carrying, at its other end, a piston 34 slidable in a cylinder 36 secured, through an adapter 38, to the engine nosedi). The elementsI2, I4, I6 and 20 comprise a conventional form of reduction gear inwhich the sunfgear 20 is substantially fixed and is subject to reactionforces from the driving effort in proportion to the torque transmitted.Accordingly, the compressive load on-the :strut 32, during operation, isproportional to engine torque. The stop 30 is adjusted for clearance sothat the sun gear 20 with its projection 28 has slight circumferentialfreedom by which the piston 34 5 may move with respect to the cylinder36. TheI latter is provided with relief slots 40, as clearly shown inFig 4, and the piston 34 is so adjusted as to open or close these slots.The cover of the cylinder 36 carries a ilask -42 communicating i througha passage 43 with the cylinder interior,

a valve 44 being provided in the passage 43 for adjustment of the rateof fluid flow between the flask and cylinder. Also, into the cylinderfluid is fed from a line 45 leading from a'pump 46,

l the intake side of latter being fed from an oil supply line 41 havingan air bleed 48 therein. The cylinder 3'6 communicates, Vthrough anadthe sun gear is reached and the gauge 52 accordingly will register areading proportional to v20 justable orifice 50, with a pressure gauge52 which may be calibrated to indicate torque. As a torque meter, theappar-tus described functions as follows: A relatively uniform volume ofoil and air is fed by the pump 46 to the cylinder 36, and

this fluid bullas up in pressure to the extent necessary to move thepiston 34 against engine torque until the relief slots 40 uncover. Whenthe siots open, the pressure in the cylinder 36 will be relieved until abalance with torque reaction on torque.

Now, the flask 42 will gradually i'lll with air, the air entering withthe oil gravitationally separating from the latter, excess air and oilbeing discharged through the slots in the cylinder 35 36. The air in theflask will be maintained at a 40"augmented flexibility.

Fig. 3 shows a modiication in which the cylinder, designated as 36',carries a flask 42' ltherebelow, the passage 43' between the cylinderand flask entering the top of the latter. When using 4,. this device,the air bleed shown in Fig. 1 need not be used, since the flask 42' willll up with oil and the liquid oil will act as the spring in placel ofthe' air in -the ask 42. Since the volumetric modulus of elasticity ofliquid oil is many times higher than that of air, thevolumetric-capacity of the oil ask 42' must necessarily be much greaterthan that of the nair flask 42 to obtain analogous spring action.

- Primary calculations as to the pressure in and 5 size of flasksnecessary for oil and air respectively, have been made for a typicalvgeared aircraft engine of around 1,000 H. P. When using oil, a flaskvolume of 360 cu. in. under 4,000 lbs./ sq. in. pressure would serve tohave the desired d effect in altering the natural frequency of the shaftsystem to such an extent as to avoid any possibility of resonance in thesystem at operate ing speeds. 1

Using air in the ilasks, a flask volumevof 140 65 cu. in. at 200 lbs/sq.in. pressure, would serve the same purpose. Variations in the capacityof the flasks with inverse variations of the pressures necessary arereadily calculable to provide operative vibration dampers. A fluidspring of the 70 character herein taught is4 enormously lighter and morecompact than metallic springs of equivalent capacity and flexibility,and is not subject to fatigue failure. Also, the pressure produced inthe fluid spring, as indicated, is useful in measu uring torquetransmitted.

While I have described my invention in detail in' its present preferredembodiment, it will be obvious to those skilled in the art, afterunderstanding my invention, that various changes and modifications maybe made therein Without departing from the spirit or scope thereof. Iaim in the appended claims to cover all such modifications and changes.

What I claim is:

l. In a power plant crankshaft-propeller system, a reduction gearbetween the shaft` and propeller including a reaction gear, and meansfor reducing the natural torsional period of the shaft system comprisinga reservoir for elastic fluid, a cylinder communicating therewith, apiston engaged -by `the reaction gear and urged thereby into saidcylinder to compress the fluid in said reservoir, and means to add orremove fluid to or from the reservoir to maintain same at constantvolume regardless of changes in the pressure imposed thereon.

2. In a Powerplant crankshaft-propeller system, a reduction gear betweenthe shaft and propeller including a reaction gear, and means for,reducing the natural torsional period of the shaft system comprising areservoir for elastic fluid, a cylinder communicating therewith, apiston engaged by .the reaction gear and urged thereby into saidcylinder to compress the uid in said reservoir, and means formaintaining the reservoir-cylinder system at constant volume under thevarious pressures imposed on the uid therein by Various force reactionson said reaction gear.

3. In a transmission system including a heusing, a drive shaft and aconcentric driven shaft having a reduction gear therebetween, saidreduction gear including an oscillatable but nonrotative reaction memberheld by said housing, means for reducing the natural vibration frequencyof said shaft system comprising a substantially -constant Volume .ofelastic fluid conned in said housing and compressed by said reactionmember, and means to maintain the fluid at constant volume under alloperating conditions.

4. In a transmission system including a housing, a drive shaft and aconcentric driven shaft having a reduction geartherebetween, saidreduction gear including an oscillatable but nonrotative reaction memberheld by said housing, means for reducing the natural vibration frequencyof said shaft system comprising a housing carried constant volumecontainer having elastic fluid therein, mechanism actuated by' saidreaction member for imposing pressure on said iluid proportional to theforce reaction of. vsaid member, and means for adding or removing fluidto or from thecontainer to maintain. the container full of the elasticfluid at all times.

5. In a transmission system including a housing, a drive shaft and aconcentric driven shaft having a reduction gear therebetween, saidreduction gear including an oscillatable but nonrotative reaction memberheld by said housing,

and means for reducing the natural vibration frequency of said shaftsystem comprising a` and a driven shaft connected by a reduction gearthereto, the reduction gear including a reaction element, a pistonconnected to said element, a cylinder within which said piston engagesand 5 having relief ports unooverable by said piston,

said cylinder comprising a chamber of considerable volumetric capacity,and means for feeding.

elastic iiuid under pressure to said cylinder to maintain a constantvolumethereof in the cyl- 10 inder under all operating conditions.

7. In a power plant transmission including areduction gear having anoscillatable reaction element, means for holding lsaid element againstthe torque reaction comprising a piston member 15 engaging acylindermember and containing elastic fluid, one said member being xedand the other being oscillatable with said reaction element, saidmembers comprising a chamber of a volumetric fluid capacity of suchorder that the 20 contained fluid acts as-spring to reduce the naturalfrequency of the transmission system, and

' means to add or remove elastic fluid to or from said chamber inaccordance with torque variations to maintain said chamber atsubstantially constant effective volume under all load conditions.

8. In a power plant transmission including a reduction gear having anoscillatable reaction element, means for holding said element againstthe torque reaction comprising a piston member engaging a cylindermember and con- :taining elastic fluid, one said member being xed andtheother being oscillatable with said reaction' element, said memberscomprising a chamber of a volumetric fluid capacity of suchy order thatthe contained uid acts as spring to reduce the natural vibrationfrequency of theltransmission system, and means to maintain said uid ata pressure substantially proportional to the torque transmitted, and toadd or remove uid to or from said chamber in accordance with `torquevariations izo-maintain said chamber at substantially constant effectivevolume under all load conditions.

EDWARD S. TAYLOR.

